[MC-94289] Gradually increasing server lag ends in crash

Server lag gradually increases over time, eventually leading to a crash.

I usually just restart the server when lag becomes unbearable. I can play for several hours without noticeable lag when I'm alone on server. Issue escalates very quickly as the number of player increases.

Strangely enough, placing water sources seems to accelerate the problem, as I get intense lag spikes (server-side lag, not client-side) when placing source blocks, no matter where.

Reverting server to 15w47c usually solves the problem.

Attached crash log.

Related issues

duplicates

MC-94438 Server: Mob pathfinding induced massive lag in any versions 15w49a and later

Attachments

crash-2015-12-13_04.30.04-server.txt

Comments

migrated 2015-12-13T16:33:56Z

[media]

migrated 2015-12-13T17:08:16Z

Does MC-91676 describe your problem?

EarlyReflections 2015-12-13T19:13:17Z

@redstonehelper

I don't think so, but it's possible it may be related to it, idk. The crashes and increasing server lags don't seem to be stemming from flowing water/lava. MC-91676 seems to only involve flowing lava. I've experienced the flowing lava issue, especially in the nether.

In my case, I have no idea what causes the ever increasing server lag. I've mentioned lag spikes caused by placing water sources, but already flowing water doesn't seem to be an issue. Placing water sources that initiate flowing DO cause very major lag spikes though, server-side (when I place a water source, everyone experiences the spike).

The problem has all the symptoms of a very bad memory leak, but I have no tools to monitor/confirm that on my rented host, which is a basic 1 GB package. I will ask for a CPU and RAM meter on my Multicraft panel, but I've been told that those are quite inaccurate and next to useless.

The lag increases gradually just by playing and running around very normally. A server-side TPS meter would be a useful tool to have in the debug screen. I think it would help in isolating the cause of the issue.

I found no way to reproduce the issue. I just have to "play" and wait for it to happen. Although, like I said, the problem arises exponentially faster as more players are online. Most of the times I'm all alone and the problem can take several hours to show up.

EarlyReflections 2015-12-18T02:16:15Z

I have a hard time believing I'm alone with this problem. 51b is even worse. This is not a host issue, otherwise previous versions would also exhibit the problem. I've restarted the server 3 times, only today, and all 3 times I was alone casually playing on it.

At one point, it took a zombie a full minute to walk 12 blocks towards me.

I have the impression it has to do with the mob A.I. because it's A LOT worse during nighttime.

Any clues?

EarlyReflections 2016-01-20T20:49:31Z

This is definitely related to MC-94438, probably even a duplicate.